Bulbing Fennel - Knowledgebase Question

Ionia, NY
Question by tecchef
June 10, 1999
Last year I planted some Florence Fennel and it did quite well; however it never really produced a defined bulb instead it formed a long and deep root. I snipped off seed pods as they formed but it still never really formed a bulb. How do I force a bulb rather than a root stem like I got? Is there a better bulbing variety?

Answer from NGA
June 10, 1999


Fennel is a semihardy perennial, developing stems similar to celery and a root similar to carrot. If allowed to winter over, the base of the plant will become larger, but it will never be large and round like kohlrabi.

Fennel, a graceful and bushy plant, is one of the oldest known culinary herbs; its anise-flavored leaves and seeds are highly valued in fish cookery. It is a perennial, growing 3 to 4 feet tall, with a thick, glossy main stem and feathery leaves; in summer these are topped by clusters of tiny yellow flowers. By midsummer these clusters begin to droop under the weight of their brown, ribbed seeds, almost 1/2 inch long, that give off a strong, sweet scent.

Fennel, though a perennial, can be grown as an annual in all zones. It does best in full sun, in any garden soil with a pH of 6.0 to 8.0, supplemented by 5-10-5 fertilizer in the amount of 3 ounces to 10 feet of row

Sow fennel seeds in early spring if you want to harvest seeds as well as leaves. If you grow the plant for its leaves alone, the seeds can be sown continuously at 10-day intervals until summer, assuring a continuous fresh supply. Fennel can also be propagated by root division in the early spring.

Harvest the thick bulbous stem in late fall. Barely cover seeds with a thin layer of soil, and when the seedlings are 2 inches high, thin or transplant them to stand about 1 foot apart. Unless it is growing near a fence or a wall, fennel may need to be staked when it gets tall, to protect it from strong winds. Fennel flower heads should be cut before they bloom if the plant is being grown for its leaves alone; this encourages greater leaf growth and the development of a thicker base. When the bulbous base is about the size of an egg, cover it with soil halfway up, to blanch it. The base will be ready for harvesting in about two weeks.

Fennel leaves can be harvested continuously from the time the flower heads form until just before the first frost. Use them fresh or dry them in the shade, then store them in an airtight container. Harvest fennel seeds when they ripen, in the fall, and spread them in a thin layer on a screen in the shade to dry, turning them often.

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